Electronic emission



H. P. DONLE ELECTRONIC EMISSION Filed .Fb. 5. 1923 gig.

Dec., l

pending application Serial No.'295,897, filed Pawnee ec. is; 19232;..v

f ITED STATI:

time@ r ou.

HAROLD PONTER DONLE, OF MERIDEN, CONNECTICUT, AssIGNoR To THE ooNNnorrCU'r mEnmHoNE AND ELECTRIC COMPANY,

CUT, A CORPORATION lOl? CONNECTICUT.

INCORPORATED, F MERIDEN, CONNECTE- ELECTRONIC niaissIoN.

Application filed February 3, 1923. Serial No. 616360.

To all whom tmay concern:

Be it known that I, HAROLD P. DONLE, a citizen of the United States of America, and residing at Meriden in the county of New Haven and State ci Connecticut,.have invented .new and useful Improvements in Electronic Emission, of which the following is a Specification. y

The object of my present invention is `to increase the .operating eectiveness of vacuum tube apparatus having heated elecL tron-emitting cathodes. According to this invention -Lprovide metallic ions Within the tube and thus, in addition to furnishing a 1.5 basis for ionization effects, increase the electron emission 'ofthe cathode for a given temperature.

This is a partial continuation of my c'oay 9, 1919.` I have discovered that metallic Vions may .conveniently be 'electrolyzed from the glass wall of the vacuum tube it.

self. When said tube is made of soda glass,

\ 'fsodium ions areutilized:d When a potash 26 glass is used, potassium ions are released.

The increase of filament electron emission referred to .above appears to be due toa deposit of such alkali metals upon the cathode itself.t lt is not" difficult to appre- 30 ciate thati positively charged molecules of sodium or potassium, for instance, are released. Within the evacuated space of a tube containing anode and cathode, they Will be attracted to and deposited upon the cathode.v 35, There the electric charge of the ions will necessarily be neutralized and the molecules Will constitute a simple metallic coating upon the cathode surface. `The e'ects may be better understood from. al consideration of the accompanying drawings Where v Figs 1, 2 and 3 illustrate three stages of rai-*demonstration showing the described -in- Vcrease'of electron emission. f -F'g. 4 is a graphic illustration of the comparative resultsunder the conditions vot' Fig. 1 andFig. 3,' and vFig. 5 showsa tube connected in :one of the usual circuitsutil-i'zed fortvvo-electrode radio receivers. r. f The vacuum tube'ff? Shown in Figs. 1, 2, 3 and`5- contains a lamentary cathode 9 and a spiral anode 10. 'llhe filament may beet highly refractory metals such as molybdenum, tungsten or tantalum, In Figs. 1, 2

ture. Control of such heating may also be had by means of a resistor in series with the battery A, 1n the usual vvay. A second bat- 'tery B, with potentiometer, is also provided for supplying a controllable 'potential (measf ured from the negative terminal of the cath- 0de 9) to the anode 10. l

When the cathode 9 is heated to'normal "temperature, the anode Vpotential of thc newly-manufactured tube (represented in Fig. 1) -may be varied from say 0 to 40 volts, with connections as shown, and for each anode potential the anode circuit current maybe measured by means of ammeter 12. For a particular tube tested in this way it was found that the anode current gradually increased-from 0 to 100 microamperes as the potential was increased from 0 to approxif mately 5 volts, but that this maximum-or saturation value of current did not increase with further increments of voltafgeup to a valueas high as 4:0. lt is generally understood that a limitatiomot current yunder these conditions is due to a lack of electrons emitted from the cathode, there being' only enough electrons in this instance to carry 100 microamperes. In the particular form shown the tube 7 carries in contact with a portion of its outer surface a secondary anode 11. This external electrode may be a band of silver or Otherf'metal of like characteristics, applied directly to the outside of the Wall of the tube. ln Fig. 2 the anode battery B is shown connected to this sec-'- ondary anode 11, by means of the wire 15,

the Working anode ltlbeing left free. rl[`he lamentary cathode is heated as before, and

v the secondary anode potential set at a convenient value. Underthese 'conditions the heated glass wall of the tube ermits the passage of electrons from t e cathode through the glass to the external anode, the

glass being partly dissociated and, it soda 35 the same as in the 'rst test,'it isevident gieee is used, e-ediem iene thee preddeed being thrown oi into space. TheseA ions are positively charged, hence'some necessarily travel to the ilamentary cathode and form a coating thereon. A certain amount of sodium travels, either directly or after evaportion from the cathode, to the cooler parts ionization. l lHaving continued treatment using the4 connections of Fig. 2 :for about live minutes the bright deposit described becomes relatively heavy and practically opaque- If the '20 eanode connection. 15 isnow attached to. the

working anode 10, as in Fig. 3, another series 'of measurements of anode current for various voltages may be taken. having been treated -as explained, it is found that for a given cathode temperature and anode potential the anode-current` is much greater. The same tube described in' connection with Fig. 1 was so treated, and

then remeasured las in Fig. 3; Vtheanode currentrose to 2400 microamperes as the potential was increased from 0 to about 24 volts, at which point saturation was reached and the supply of electrons exhausted. --The lament temperature being that the `emission has been increased some 2li-fold by the treatment. YThe measurements are represented' by curves'14 (before treatment) and. 17 (after treatment) in Fig'. 4.

The vacuum at 8was kept inoperation during the three `parts of the demonstration 'illustratedsby that might have 'been present.

Figs. 1, 2 and 3, so as to maintain the highest possible vacuum and to remove any gases tion did not prevent the vformation ofthe current through the wall of the tube dur' metallic deposits described.

I have found that an increase of produced in this way is not necessarily permanent. Thev time the -eiect will persist depends upon the composition of the glass and the temperature at which the filament is run after treatment, but usually the ef? Afeet willA last for some time before beginning-A gradually to fall oi. However, it is .entn'ely feasible to maintain the conditionof maximum emission by maintaining a supply of suitable metallic ions vwithin the tube. 'This may be done by continuously passing ling vits periods of operation and 'thus 'renew-A ing the'depositupon the cathode by the substantially continuous electrolytic dissociation of the currentfcarrying glass andthe:

The tube pump connectedlto the tube This operaemission i consequent liberation of sodium,l potassium orthe like.

The arrangement of Fig. 5 means f or maintaining a suita le condition withinthe tube in this way. The working anode 10 is here-provided with `a positive rovides one potential derived from the battery A by way of a4 potentiometer 18, and an aerial 19. and telephone receiver 20 are associated with the detector 'tube in the Ausual way.

The external electrode isV supplied with curv 4rent from battery. B through potentiometer 13, as in Fig.'2, andserves to furnish metallic. ions while the' tube is in operation. The supply of ions for deposition upon the cathode maybe augmented by ions produced -when electrons: from the cathode strike, with suiiicient velocity, neutral molecules of the metallic ,vapor or atmosphere produced Within the tube by partial evapo-r ration vof the deposits on the filament orV walls under the iniiuence of heat.

I have found that the increased emission leil-'ect vdescribed permits substantial economies in the energy consumed by the filament of a, vacuum tube detector, and that the provision of metallic ions permits the use of desirable ionizationeifects common in vacuum tubes containing residual gas. However, vin tubes supplied with metallic ions theseelfects are stabilized to so great' an extent that they may be depended upon -to' produce uniformly a higher sensitiveness than can be secured from the critical and transient ionization phenomena in detector tubes containing residual gas. More-V over, such metallic ionization tubes as I have described may be lmamifactured in large quantities with practical uniformity, and are not subject to'thewide variat1ons whichoccur in the production .of prior art tubes intended to utigliz'e 'non-metallic gaseous ionization.-

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n win be noted. that' the tubes deeeribed have anunobstructed path for electrons an ions between'A thelcathode 9 and working anode 1 0, andl consequently that`- the conduction and other eiects' taking place in the space between the 'electrodes Aare not interfered with or complicated. by changescin field intensity-'or potential gradient which might be introduced by the addition of any interposed electrodes, shields or other ob- .'stacles.. By the provision. of this free electronic and ionic zone the control of the phenomena utilized in my tubes v' ionization is facilitat A To maintain .the condition `g,1;iving risetoA the effects characterized by increased cathodic emission 'I may rely in part upon ionizthe tube;- -The supply of ions thus secured serves -to augment those produced directly by .electrolytc dissociation within, the tube ationof deposited bodies of sodium, potas .sium or the-like upon the interior wall of' remesa y Walls. The proportion of the total ionization required for this effect from either A source may be varied, and I may supplement or add to the internal deposit by introducing a suitablevmetal or metals during manufacture of the tube. In fact many desirable and novel eects may be produced by introducing sodium, potassium ory the like, into the tube instead of relying upon elec-I trolysis during or after exhaustion.

It should be understood that many advantages of metallic ionization as herein .set-

' and non-luminous.

forth 'may be obtained in tubes having three internal electrodes, such as are described and claimed in my original application Serial No. 295,897 or in. my applications Serial Nos. 579,828 and 604,312. The two last named applications disclose structuresv in which, as in the present case, an unobstructed path is provided for electron andY ion flow between anode and cathode.

It is characteristic ofthe ionization effects utilized by me that they are non-progressive though suflicicnt ionization Within the 4tube is produced within the tube to provide means for increasing filament electron emission',

the ionizationA is not sufficiently violent orvattracting to to secure luminous ionizationbut under such conditions the tubes are substantially if not wholly useless as detectors or amplifiers.

, I claim:

1. The method of increasing the electron emission of alamentary cathode at a given temperature which consists in continuously attracting to said cathode electrically charged particles of sodium.

2.; The method of increasing the electron emission 'of a' lamentary cathode at a given temperature which consists in Acontinuously said cathode -electrically charged particles of an alkali metal.

3. Ina radio signalling system a vacuum tube having a highly refractoryV filamentary cathode, and an anode with an unobstructed electron path therebetween, a deposit of an alkali metal Within said tube and means for maintaining a coating of alkali met-al on said cathode, all in combination with means for impressing radio frequency' potentials upon electrodes of said tube and a translating device connected thereto.

4. In aradio signalling system a Wave intercepting device, a vaccum tube having an anode and a highly refractory iilamentary cathode with a coating ofalkali metal,

and 'a translating device operatively connected therewith.

HARLD PT'IER DONLE. 

